Aerial refueling is commonly employed to increase the range and flight duration of an aircraft. Some types of aerial refueling systems include a hose having a drogue attached thereto which trails or drags behind a fuel tanker. On the end of the hose is a “basket” which includes a reception coupling. The receiver aircraft includes a probe (or fuel inlet) that may be fixed or retractable. When the receiver aircraft needs to be aerial refueled, it approaches the tanker and then flies formation on the trailing aerial refueling hose, slowly approaching the reception coupling. Eventually the receiving aircraft “stabs” or engages the probe into the reception coupling, thereby providing a connection for transferring fuel between the tanker and the receiver aircraft. Known hose and drogue aerial refueling systems include, for example, those systems disclosed by U.S. Pat. No. 5,573,206 issued to Ward, and U.S. Pat. No. 5,539,624 issued to Dougherty.
Typically, in order to initiate the tanker refueling pumps to commence the fuel transfer from the tanker to the receiver aircraft, the receiver aircraft must engage the probe into the refueling hose coupling and push the hose in past the outer refueling limit. The receiver can push beyond the minimum to receive fuel from the tanker. Fuel flow will continue as long as the receiver aircraft keeps the hose in the “refueling envelope”. Typically the receiver aircraft pushes to a range, somewhere in the middle of the refueling envelope. If the receiver aircraft pushes the hose in to the inner refueling limit, the tanker fuel system will shut down, ceasing fuel transfer to the receiver aircraft. If the receiver aircraft pulls out to where it is back in the refueling envelope, fuel transfer will reinitiate. Upon completion of the refueling process, the receiver aircraft continues to back out until the tanker hose is fully deployed. At this point, if the receiver aircraft backs out further, the connection between the tanker reception coupling and the receiver aircraft probe is released. During this whole process, as the receiver aircraft pushes and pulls on the hose, the tanker hose reel system winds and unwinds the hose on a tanker mounted hose reel to keep the slack out of the hose.
Although desirable results have been achieved using prior art aerial refueling systems, some drawbacks have been noted. For example, during some operating conditions, the refueling hose may be difficult for the personnel on board the receiver aircraft to see. Glints, shadows and glare caused by the sun, atmospheric water vapor, or reflections from aircraft surfaces may hamper visibility of the refueling hose during daylight operations. Similarly, darkness or relatively low lighting conditions may obscure visibility of the refueling hose during nighttime operations. Furthermore, the markings that are normally placed on the hose to designate the inner, center, and outer refueling envelope may be equally difficult to observe. Thus, there exists a need for an improved aerial refueling system that reduces adverse viewing conditions and improves the ability of the personnel on the receiver aircraft to view the refueling hose during varying lighting conditions.